The present invention relates to information dissemination systems, and more specifically to data source hand-off in broadcast-based data dissemination environments.
Nearly everyone uses broadcast-based information systems to receive information and entertainment in their day-to-day lives. For example, radio and television stations broadcast music, pictures, and news programs across the country to radios and television sets. Broadcast-based systems are typically characterized by a single data source disseminating information to many data receivers. Unlike many request-response type information systems, information in a broadcast-based system, in general, travels in one direction from a data source to a data receiver. In other words, the data source of a broadcast-based information system does not wait for a response from the data receiver before sending more information.
The xe2x80x9cone-wayxe2x80x9d path of information from the data source to the data receiver of a broadcast-based system enables information to be sent to many subscribers in a relatively quick and inexpensive manner. Although this attribute enables efficient transfer of information, subscribers within the system give up the flexibility of choosing the arrival time and the individual content delivered over the broadcast channel. Because of this tradeoff between efficiency and flexibility, broadcast systems are generally arranged to provide different data on different data channels to meet the varied needs and preferences of its audience. For instance, many radio stations focus their broadcast on a specific area of interest, such as news, sports, or country music. Depending on individual tastes and interests, radio listeners choose the type of program to receive by tuning their radio receivers to their preferred stations. Thus, radio listeners do not have direct control over the content of each data channel, only the freedom to choose another data channel to listen to.
In general, data signals of traditional broadcast-based information systems have a limited geographic broadcast range. When a subscriber travels beyond the data signal""s broadcast range, a new data source covering the local geographic area must be selected in order to maintain data reception. Moreover, if a subscriber wishes to continue receiving similar data content, the broadcast system must be searched to find a local data source providing such content. For example, if a radio tuned to a country radio station moves too far from the radio station, the signal will become too weak and a new radio station must be selected to maintain radio reception. Furthermore, if the listener wishes to continue listening to a country station, he or she may have to search the radio band to find another country station. Thus, a shortcoming of traditional broadcast-based information systems is the difficulty in receiving consistent data from one geographic region to another.
One known method of continuously carrying on a communication link from region to region is called hand-off. Hand-off is typically associated with cellular telephone communication. A cellular telephone network typically divides a geographic area into a cellular grid. A base station controls telephone communications within each cell in the grid, and wireless phones within a cell transmit and receive data to and from the cell""s base station. When a wireless phone physically crosses a cell boundary and moves to a new cell in the grid, the base station in the old cell disconnects from the phone and a base station in the new cell takes over communications with the phone. This process is referred to as xe2x80x9chanding-offxe2x80x9d and, if all goes well, occurs without the phone user ever knowing that it is happening. To the user, the phone call appears as a continuous connection to the party at the other end of the line.
The type of hand-off described above is generally referred to as a horizontal hand-off. Another type of communication hand-off called vertical hand-off has emerged in recent years. The concept of vertical hand-off is similar to horizontal hand-off, except that communication cells are configured to overlap on top of each other, as opposed to being placed adjacent to each other. Typically, a small cell is used to cover the area of buildings, and a larger overlapping umbrella cell is used to cover the distances between buildings. When a mobile user enters or leaves a building, the connection between the user""s wireless phone is switched over to the area""s base station without dropping the voice conversation.
Another drawback of traditional broadcasting-based information systems is their inability to provide specific information tailored to the particular area around the listener""s location. Returning to the example of a radio listener traveling across a broadcast area, the listener may be interested in listening to advertising or traffic conditions within ten square blocks of his or her location. With current radio broadcasting methods, the listener must listen to all information broadcast by the radio station, no matter how irrelevant it is to the listener.
The present invention addresses the above-mentioned limitations of traditional broadcast-based data dissemination systems by teaching a method, system, and apparatus for handing-off data receivers in a broadcast-based environment. Data receiver hand-off is carried out between data sources in different data cells broadcasting information of the same category. Furthermore, data cell ranges are based on geographic regions rather than signal strength coverage. Briefly stated, the hand-off process involves acquiring the current receiver location of the data receiver and comparing the receiver location with a current data cell range. If the current receiver location is outside the current data cell range, a hand-off controller searches for a new data source encompassing the current receiver location coordinates and having an associated data topic matching the current topic. Once a new data source is found, the hand-off controller subscribes the data receiver to the new data source.
Thus, an aspect of the present invention involves a method for delivering data streams categorized by topic to at least one data receiver in a broadcast-based data dissemination environment. The method includes defining a first data cell range based on a first geographic region and defining a second data cell range based on a second geographic region. A subscribing step subscribes the data receiver to a first data source when the data receiver is located at a first receiver position within the first data cell range. The first data source broadcasts a first data stream across a first data channel, and a topic categorizes the first data stream. A detecting step detects when the data receiver is located at a second receiver position outside the first data cell range and within the second data cell range. Another subscribing step subscribes the data receiver to a second data source when the data receiver is located at the second receiver position. The second data source broadcasts a second data stream across a second data channel, with the second data stream having the same topic subject as the first data stream.
Another aspect of the invention is a broadcast-based data dissemination system. The system includes a first data source having an associated first data cell range. The first data cell range is defined by a first geographic region and is associated to a first data topic. The first data source is further configured to broadcast a first data stream across a first data channel. The system additionally includes a data receiver having a current receiver location and subscribing to the first data source. A second data cell range defined by a second geographic region is associated to a second data source. The second data source is also associated to a second data topic matching the first data topic and is configured to broadcast a second data stream across a second data channel. A hand-off controller is configured to subscribe the data receiver to the second data source if the current receiver position changes from the first data cell range to the second data cell range.
Another aspect of the invention is a data structure stored in a computer-readable medium. The data structure includes a primary data source identifier field identifying data sources within a broadcast-based data dissemination environment. A data cell range field is coupled to the data source identifier field and describes geographical ranges of data cells controlled by the data sources. A communication link field is also coupled to the data source identifier field and describes data channels for receiving data streams from the data sources.
The data structure may further include a topics field which identifies data sources broadcasting data with a common topic. Furthermore, the data structure may be configured with a data receiver identifier field, a location information field, and a secondary data source identifier field. The data receiver identifier field identifies data receivers within the broadcast-based data dissemination environment. The location information field is coupled to the data receiver identifier field, and describes geographical locations of the data receivers. Finally, the secondary data source identifier field is also coupled to the location information field and identifies data sources subscribed to by the data receivers.
Another implementation of the present invention is a method for handing-off a data receiver to a data source in a broadcast-based data dissemination environment. The data receiver is positioned at a current receiver location and receives a current data stream from a current data source. The current data source has a current topic and a current data cell range, with a geographic region defining the current data cell range. The method includes acquiring the current receiver location of the data receiver. A comparing step compares the current receiver location with the current data cell range. If the current receiver location is outside the current data cell range, a searching step searches for a new data source having an associated new data cell range encompassing the current location coordinates and an associated data topic matching the current topic. A subscribing step then subscribes the data receiver to the new data source.
Yet another aspect of the invention is a data receiver configured to present a data stream from a data source in a broadcast-based data dissemination environment to a user. The data receiver includes a position sensor configured to sense the current geographical location of the data receiver. A broadcast receiver is configured to receive a current data stream from a current data source. The current data source has a current topic and a current data cell range, with the current data cell range defined by a current geographic region. The data receiver also includes a data source table identifying data sources, data cell ranges, and data channels within the broadcast-based data dissemination environment. In addition, a hand-off controller configured to subscribe the data receiver to a new data source listed in the data source table is used when the current geographical location of the data receiver falls outside the current data cell range. The new data source has an associated new data cell range encompassing the current geographical location of the data receiver and an associated data topic matching the current topic.
The foregoing and other features, utilities and advantages of the invention will be apparent from the following more particular description of various embodiments of the invention as illustrated in the accompanying drawings.